Does Intra-Abdominal Adipose Tissue in Black Men Determine Whether NIDDM Is Insulin-Resistant or Insulin-Sensitive?

Insulin resistance in black Americans with non-insulin-dependent diabetes mellitus (NIDDM) is found in only 60% of those with a body mass index (BMI) of <30 kg/m², suggesting that NIDDM can occur independent of peripheral insulin resistance. When insulin resistance is present, it is not necessarily correlated with obesity. Numerous studies have shown that increased amounts of intra-abdominal adipose tissue are associated with various metabolic abnormalities. We therefore investigated whether the occurrence of insulin resistance in black NIDDM men could be explained by the pattern of body adipose tissue distribution rather than total adiposity. Twenty-two near-normoglycemic black men (fasting plasma glucose [mean ± SD] = 104 ± 10 mg/dl, HbA_1c = 4.6 ± 0.78%, age 48.9 ± 9.2 years, and BMI 26.5 ± 2.4 kg/m²) were studied. The euglycemic insulin clamp with 1 mU · kg⁻¹ · min⁻¹ insulin infusion and D-[3-³H]glucose was used to measure insulin action. Whole-body computed tomography with 22 scans was used to determine body composition. Total body adipose tissue was 19.6 ± 7.5 1, and the percentage of body fat was 27 ± 7. Glucose disposal ranged from 2.5 to 8.1 mg · kg⁻¹ · min⁻¹ (10 men were insulin-sensitive and 12 were insulin-resistant). There was a strong inverse correlation between glucose disposal and the proportion of total adipose tissue in the intra-abdominal region (r = −0.78, P < 0.001), while there was no correlation between glucose disposal and total muscle volume, BMI, total adipose tissue volume, or total subcutaneous adipose tissue volume. When insulin resistance is present, it is highly correlated with an increase in the proportion of intra-abdominal adipose tissue. The data raise the possibility that insulin resistance in black NIDDM men may be a consequence of increased intra-abdominal adipose tissue mass.